We recently developed the new Dynamic Light Scattering (DLS) Clinical device under the NASA-NEI Inter-Agency Agreement, and have used it in several cataract studies on more than 400 patients. We found that the DLS cataract data correlate well with Clinical and Photographic Cataract Grading scales, and that the reproducibility is good, with error rates of less than 5%. We also found that it can detect the earliest molecular changes in lens aging and in cataract formation in patients in vivo, non-invasively.[unreadable] In this pilot longitudinal cataract study, we are using this new DLS clinical device to study 15 patients with early Pre-Senile cataract. These cataracts are morphologically similar to age related cataracts but develop in patients below the age of 55 years of age (hence "Pre-Senile"). The Principal Investigator (MDMD) observed in clinical practice that many of these pre senile cataracts develop rapidly, requiring Cataract/IOL surgery within a year or two. The other eye in most cases develops a similar cataract after the first eye, and therefore may be studied early with this device. This study aims to conduct a longitudinal follow up to detect the earliest lens protein molecular changes that occur in the living eye of these patients as the cataract develops. [unreadable] 15 Patients who developed cataract before 55 years of age, with one of the three main types of cataract - Nuclear, Cortical and Posterior Subcapsular cataracts - were screened, recruited and asked to commit to return every 1-3 months for regular follow up for 2 years or until the cataract is removed surgically. All patients gave full informed consent according to the NEI IRB approved protocol, and were advised that they can withdraw from the study anytime. At each visit, a complete dilated eye examination (including A Scan utrasonography at the initial visit), AREDS Clinical Grading of the cataract, AREDS Lens Photography, and DLS testing were performed. The DLS data is then sent to our collaborators at The NASA-John Glenn Research Center in Cleveland, Ohio (Drs. Rafat Ansari and Kwang Suh) for data analysis. [unreadable] Preliminary results confirm the rapidity of the cataract progression, as a majority of the cataracts have significantly progressed and 8 of the 15 patients have undergone cataract surgery. This type of cataract also undergoes a stage where there is lens epithelial decompensation with edema, apoptosis and scarring of the lens epithelial cell layer. We are currently prforming the complete analysis of the data.[unreadable] This type of lens clinical study has not been possible in the past because no clinical device has been developed to study molecular changes in the lens safely, reproducibly and non-invasively with the lens in-situ, without taking the lens outside of the eye. This pilot study helps to show that the DLS device can now be used for cross sectional and longitudinal studies of cataract in vivo (clinically), including for the measurement of the efficacy of newly developed anti cataract drugs in clinical trials.